Full userland debug information (MKDEBUG, see mk.conf(5)) available. While most install media do not come with them (for size reasons), the debug and xdebug sets can be downloaded and extracted as needed later. They provide full symbol information for all base system and X binaries and libraries and allow better error reporting and (userland) crash analysis.

Many evbarm kernels now use FDT (flat device tree) information (loadable at boot time from an external file) for device configuration, the number of kernels has decreased but the number of boards has vastly increased.
Lots of updates to 3rd party software included:

GCC 5.5 with support for Address Sanitizer and Undefined Behavior Sanitizer